radiant heat, boilers and heat exchangers

[Buster]

I have a 6 zone radiant heat system with a boiler attached.

4 zones are for the basement, and 2 are for the garage.

(The main floor and upper floors are forced air).

I've noticed that in very cold temperatures, the radiant heat (in slab) in the basement struggles to keep up.

Because the radiant heat is fed by poly-B in the basement, the system is two closed loops (not sure the terminology here). With the "boiler loop" isolated from the "radiant loop" that has all of the poly-B hosing in it. Sounds good- protected from oxygenation and corrosion.

The problem seems to be that the average temperature of the water on the radiant side seems quite low, and the average temperature on the boiler loop seems quite high (70C vs around 40C). From what I can tell, the heat exchanger is not able to increase the radiant loop temperature enough in colder weather.

Has anyone encountered this problem? Are there better heat exchangers? Do heat exchangers wear/corrode over time causing a degradation? Is this type of low efficiency common for a heat exchanger?

Plumbers?

[spike98]

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Do heat exchangers wear/corrode over time causing a degradation?

They most certainly can given Calgary's hard water. They become calcified and can lose efficiency. You might be able to clean it or may require a replacement.

[Buster]

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They most certainly can given Calgary's hard water. They become calcified and can lose efficiency. You might be able to clean it or may require a replacement.

Thanks for the note. Do you recommend anyone in town that can inspect/service/clean/replace the exchanger?

[benyl]

Are your valves actually opening? I had to replace 2 valves recently for the Ensuite and secondary washroom floors. They were stuck open and only got heat when another zone demanded it.

The system is closed, calcium deposits should remain static unless you have a leak and new water is being introduced (mo logic anyway). If you have a leak, that is a bigger problem as your Glycol will also start to be diluted as it leaks out.

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Thanks for the note. Do you recommend anyone in town that can inspect/service/clean/replace the exchanger?

I went with Canyon Plumbing because they did the install. My last service / cleaning cost $2K with the valves.

[Buster]

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Are your valves actually opening? I had to replace 2 valves recently for the Ensuite and secondary washroom floors. They were stuck open and only got heat when another zone demanded it.

The system is closed, calcium deposits should remain static unless you have a leak and new water is being introduced (mo logic anyway). If you have a leak, that is a bigger problem as your Glycol will also start to be diluted as it leaks out.

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I went with Canyon Plumbing because they did the install. My last service / cleaning cost $2K with the valves.

I'm going to get up there with some masking tape and my IR thermometer to test. But I'm pretty sure they are functioning normally. The temperature of the water coming out of the heat exchanger on the "house/radiant" loop is quite low. 40C. The boiler loop temperature is close to 70C. So the delta-T between the boiler loop and the radiant loop is quite high.

[ExtraSlow]

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I'm going to get up there with some masking tape and my IR thermometer to test. But I'm pretty sure they are functioning normally. The temperature of the water coming out of the heat exchanger on the "house/radiant" loop is quite low. 40C. The boiler loop temperature is close to 70C. So the delta-T between the boiler loop and the radiant loop is quite high.

What was that delta-t when the system was new?

[Buster]

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What was that delta-t when the system was new?

Good question...unfortunately it's pretty old, so I can't get that data. But a 30C delta-t is, I'm sure, WAY out of the exchanger's expected performance.

[tcon]

Scaling probably. Acid wash that HX and you'll notice an improvement guaranteed

[Buster]

I dont see any obvious way to isolate the exchanger to pull it off and do any maintenance to it. Given that it is almost acceptable in terms of performance, I'm wondering if I should wait until the weather is warmer before messing with it.

[ThePenIsMightier]

"Poly-B" as in polybutylene plastic? It's leaking. That's what it does. That stuff is trash in an ideal scenario and when you stick it in concrete it's even worse. That and your exchanger is getting fouled with mineral deposits.
Leave it until warmer and investigate then.
-1 for Canyon Plumbing. They have some good people but they also have some failed coat hanger abortions who can't follow basic code for drain distances and will plumb a toilet with hot water. Your problem is too complex to risk the wrong simpleton showing up.